Institutional Publications
Permanent URI for this collectionhttps://ndkr-library.nipgr.ac.in/handle/123456789/11
Browse
6 results
Search Results
Item Interaction of the Xanthomonas effectors XopQ and XopX results in induction of rice immune responses(John Wiley & Sons, 2020) Deb, Sohini; Ghosh, Palash; Patel, Hitendra K.; Sonti, Ramesh V.Xanthomonas oryzae pv. oryzae uses several type III secretion system (T3SS) secreted effectors, namely XopN, XopQ, XopX, and XopZ, to suppress rice immune responses that are induced following treatment with cell wall degrading enzymes. Here we show that a T3SS secreted effector XopX interacts with two of the eight rice 14‐3‐3 proteins. Mutants of XopX that are defective in 14‐3‐3 binding are also defective in suppression of immune responses, suggesting that interaction with 14‐3‐3 proteins is required for suppression of host innate immunity. However, Agrobacterium mediated delivery of both XopQ and XopX into rice cells results in induction of rice immune responses. These immune responses are not observed when either protein is individually delivered into rice cells. XopQ‐ XopX induced rice immune responses are not observed with a XopX mutant that is defective in 14‐3‐3 binding. Yeast two‐ hybrid, BiFC and co‐ IP assays indicate that XopQ and XopX interact with each other. A screen for Xanthomonas effectors which can suppress XopQ‐ XopX induced rice immune responses, led to the identification of five effectors, namely XopU, XopV, XopP, XopG and AvrBs2, that could individually suppress these immune responses. These results suggest a complex interplay of Xanthomonas T3SS effectors in suppression of both pathogen triggered immunity and effector triggered immunity to promote virulence on rice.Item Dual activities of receptor-like kinase OsWAKL21.2 induce immune responses(American Society of Plant Biologists, 2020) Malukani, Kamal Kumar; Ranjan, Ashish; Hota, Shiva Jyothi; Patel, Hitendra Kumar; Sonti, Ramesh V.Plant pathogens secrete cell wall-degrading enzymes that degrade various components of the plant cell wall. Plants sense this cell wall damage as a mark of infection and induce immune responses. However, the plant functions that are involved in the elaboration of cell wall damage-induced immune responses remain poorly understood. Transcriptome analysis revealed that a rice (Oryza sativa) receptor-like kinase, WALL-ASSOCIATED KINASE-LIKE21 (OsWAKL21.2), is up-regulated following treatment with either Xanthomonas oryzae pv oryzae (a bacterial pathogen) or lipaseA/esterase (LipA; a cell wall-degrading enzyme of X. oryzae pv oryzae). Overexpression of OsWAKL21.2 in rice induces immune responses similar to those activated by LipA treatment. Down-regulation of OsWAKL21.2 attenuates LipA-mediated immune responses. Heterologous expression of OsWAKL21.2 in Arabidopsis (Arabidopsis thaliana) also activates plant immune responses. OsWAKL21.2 is a dual-activity kinase that has in vitro kinase and guanylate cyclase activities. Interestingly, kinase activity of OsWAKL21.2 is necessary to activate rice immune responses, whereas in Arabidopsis, OsWAKL21.2 guanylate cyclase activity activates these responses. Our study reveals a rice receptor kinase that activates immune responses in two different species via two different mechanisms.Item OsWAKL21, a putative receptor of rice cell wall damage activates alternate signaling in rice and Arabidopsis to induce immunity(American Phytopathological Society, 2019) Malukani, K. K.; Ranjan, A.; Hota, S. J.; Patel, H. K.; Sonti, Ramesh V.Xanthomonas oryzae pv. oryzae (Xoo) causes the serious bacterial blight disease of rice. As part of its virulence repertoire, Xoo secretes various cell wall degrading enzymes (CWDEs) such as cellulases, xylanases and a Lipase/esterase (LipA). Conversely, treatment of rice tissues with any of these purified enzymes activates immune responses. Plants sense this cell wall damage as a mark of infection and induce immune responses. Very little information is available about the plant functions that are involved in the elaboration of cell wall damage induced immune responses. Transcriptome analyses revealed a rice cell wall-associated receptor kinase, OsWAKL21 that is upregulated following treatment with either LipA or Xoo. VIGS mediated downregulation of OsWAKL21 attenuates LipA induced immune responses. Overexpression of OsWAKL21 in rice mimics LipA treatment in induction of immune responses, activation of JA pathway and enhanced expression of defence related genes, indicating that it plays an important role in elaboration of LipA induced immune responses. Ectopic expression of OsWAKL21 in Arabidopsis also activates plant immune responses. OsWAKL21 is a moonlighting kinase having in vitro kinase and guanylate cyclase activities. Interestingly, OsWAKL21 needs kinase activity to activate immune responses in rice while in Arabidopsis it needs the guanylate cyclase activity. Thus OsWAKL21 is activating similar immune responses in two different species but via different mechanisms.Item Phase variation in rice pathogen Xanthomonas oryzae pv. oryzae(American Phytopathological Society, 2019) Madhavan, V. N.; Patel, H. K.; Patil, P. B.; Sonti, Ramesh V.Xanthomonas oryzae pv. oryzae (Xoo) is the causal pathogen of bacterial blight of rice. Diverse factors contribute to its virulence, e.g., secreted enzymes, protein involved in adhesion, gene regulation. Two such studied virulence factors are Exopolysaccharide (EPS) and Lipopolysaccharide (LPS). LPS is a structural component of the outer membrane of all gram-negative bacteria. LPS is necessary for the function of many outer membrane proteins and protect the bacteria from antimicrobial plant products. EPS is a complex polymer secreted by Xanthomonas genus and the known functions of EPS include biofilm formation, and suppression of the plant immune responses. In this study, we isolated non-mucoid and virulence compromised Xoo colonies from stationary phase cultures. These spontaneous mutants are called as stationary phase variants (SPV). Our data show that, SPVs arises due to insertion of endogenous Insertion Sequence (IS) elements in EPS or LPS O-antigen biosynthetic clusters or by slipped-strand mispairing (SSM) in wxoA gene of LPS O-antigen biosynthetic cluster. The SPVs reverts to wild-type colony morphology and showed true reversion, i.e. restoration of wild-type genotype. The results suggest that we are observing phase variation in Xoo. We hypothesize that similar phase variation may be a part of Xoo’s life cycle. Which may help the bacteria survive in nutrient limited conditions during late stages of infection and on rice seeds and plant debris.Item Immune response induction in rice due to co-expression of XopQ and XopX(American Phytopathological Society, 2019) Deb, S.; Patel, H. K.; Sonti, Ramesh V.Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial blight, a serious disease of rice. Xoo uses the type III secretion system (T3SS) to suppress rice immune responses. The T3SS secreted effectors XopQ and XopX suppress rice immune responses by interaction with different rice 14-3-3 proteins. Sub-cellular localisation of XopQ and XopX mutants that are defective in 14-3-3 binding and suppression of immune responses indicates that, for suppression, XopQ requires a cytoplasmic localisation whereas XopX requires nuclear localisation. Hence, both XopQ as well as XopX individually act as suppressors of rice immune responses, probably by targeting unique pathways in different subcellular compartments. However, we find that when XopQ is delivered through Agrobacterium along with XopX, it becomes an inducer of immune responses and that it now localizes in the nucleus. We also find that XopQ and XopX can interact with each other. This raises the possibility that besides being a suppressor of immune responses, XopQ can under certain circumstances also function as an inducer of immune responses.Item Xanthomonas oryzae pv. oryzae XopQ protein suppresses rice immune responses through interaction with two 14-3-3 proteins but its phospho-null mutant induces rice immune responses and interacts with another 14-3-3 protein(John Wiley & Sons, 2019) Deb, Sohini; Gupta, Mahesh K.; Patel, Hitendra K.; Sonti, Ramesh V.Many bacterial phytopathogens employ effectors secreted through the type-III secretion system to suppress plant innate immune responses. The Xanthomonas type-III secreted non-TAL effector protein Xanthomonas outer protein Q (XopQ) exhibits homology to nucleoside hydrolases. Previous work indicated that mutations which affect the biochemical activity of XopQ fail to affect its ability to suppress rice innate immune responses, suggesting that the effector might be acting through some other pathway or mechanism. In this study, we show that XopQ interacts in yeast and in planta with two rice 14-3-3 proteins, Gf14f and Gf14g. A serine to alanine mutation (S65A) of a 14-3-3 interaction motif in XopQ abolishes the ability of XopQ to interact with the two 14-3-3 proteins and to suppress innate immunity. Surprisingly, the S65A mutant gains the ability to interact with a third 14-3-3 protein that is a negative regulator of innate immunity. The XopQS65A mutant is an inducer of rice immune responses and this property is dominant over the wild-type function of XopQ. Taken together, these results suggest that XopQ targets the rice 14-3-3 mediated immune response pathway and that its differential phosphorylation might enable interaction with alternative 14-3-3 proteins.